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Historically, enterovirus D68 (EV-D68) has only been associated with respiratory illnesses. However, in the summer of 2014 an EV-D68 outbreak coincided with a spike in polio-like Acute Flaccid Myelitis/Paralysis (AFM) cases. Statistical analysis suggested that the number of AFM cases was significantly higher during the EV-D68 outbreak than in historical controls. Among these AFM cases, EV-D68 infection was confirmed in several independent epidemiological clusters in North America, Europe, and Australia. These reports have raised concerns that the EV-D68 virus could be the causative agent of AFM during this recent outbreak.

We recently reported a phylogenetic analysis of the 2014 outbreak and found that isolates associated with AFM belong to a single phylogenetic subclade, B1. To determine if specific EV-D68 genetic determinants are associated with neuropathogenesis, we are using a neuroblastoma-derived neuronal cell line, SH-SY5Y, as a cell culture model to explore the differential infection permissibility for different EV-D68 strains. In contrast to HeLa and A549 cells, which support viral infection of all EV-D68 strains tested, SH-SY5Y cells only support infection of a subset of contemporary EV-D68 strains, including MO/14-18947 and MO/14-18949, members of the B1 subclade from the 2014 outbreak.

Viral replication and infectivity in SH-SY5Y is being assessed using four independent assays – infectious virus production, cytopathic effects, cell viability assay, and VP1 capsid protein production. In addition to supporting virus replication and other functional studies, this cell culture model may help confirm epidemiological associations between EV-D68 strains and AFM, and allow for the rapid identification of emerging neurotropic strains of EV-D68.